The present invention relates to an air-pressure molding method which is suitable for producing a vehicular door inner trim or the like comprising a shaped sheet of laminated material having a foamed resin layer as its intermediate layer.
When a vehicular door inner trim or the like is produced, according to the prior art, both a base material made of a thermoplastic resin or the like and a skin material having an integrated foamed resin layer, acting as a cushioning material are used and are so shaped and molded in advance at different steps such that they may be fitted together in the shape of the door inner trim with a foamed resin layer interposed therebetween. However, this prior art method includes the steps of shaping and molding the respective materials separately and adhering them to each other. The method thus, has a large number of steps and requires much time and work so that the production efficiency is poor.
In order to eliminate this defect, it is sufficient to shape and mold a sheet of laminated material in one step where the sheet is prepared in advance by laminating and overlying a base material and a skin material while sandwiching a foamed resin layer therebetween. However, if the laminated material is press-molded, the intermediate foamed resin layer is crushed and thus, has its cushioning performance deteriorated. If the same material is vacuum-molded, on the other hand, the intermediate foamed resin layer peels and separates from the base material and the skin material.
The applicant herein has separately proposed an air-pressure molding method which can ideally mold the aforementioned laminated material. An air-pressure molding method is provided in which the laminated material is arranged in its heated and softened state on the shaping face of a mold, and then, the portion of the laminated material to be molded is confined and hermetically sealed by a box-shaped top cover which is adapted to be moved downward. In the sealed state, the inside of the top cover is supplied, from an air pipe, with air at an air pressure higher than atmospheric pressure so that the laminated material portion is forced downward into contact with the shaping face of the mold until it is shaped and molded. In this air-pressure molding operation, air pressure can be uniformly applied downward to the entire surface of the portion of the laminated material to be molded, so that the laminated material portion can be shaped and molded to have a uniform thickness without breaking the foamed resin layer. However, the air residing between the laminated material and the shaping face of the mold forms a thin, uniform air cushion layer so that the laminated material is not forced into close contact with the shaping face of the mold. Therefore, the described air-pressure molding method is not suitable when the skin material is to have a surface which is embossed or stitched by bringing it into contact with the mold surface. If the air between the laminated material and the shaping face of the mold is merely released to the outside of the mold so as to emboss or stitch the skin surface, the laminated material is undesirably thickened especially where there is large develop- ment.